Composite body of magnesium and steel



mite Staes 3,05%,352 Patented es. 4, 19-52 ice 3,066,332 COMPQSTTE RUDY F MAGNEEUM AND STEEL l erorne J. Kanter, Pains Park, and Alvin Lahr and Ed- Ward V. Havel, Chicago, Ill, assigners to Crane (10., Chicago, ill a corporation of Illinois No Drawing. @riginal application June 4, F956, Ser. No. 557,244, new Patent No. 2,911,710, dated Nov. 10, 1959. Divided and this application Aug. 5, B59, filer. No. 831,911

8 Claims. (Cl. 29-1963.)

This invention relates, as indicated, to a composite body of magnesium and steel and the method for making same. More particularly, this invention relates to magnesium clad with a ferrous article with a eutectic compound at the interface, so that the bond between the parent materials does not come apart when deformed. The ferrous clad magnesium article of manufacture of this invention may be prepared by bonding the magnesium in the solid state.

There has been much work done in the cladding of aluminum to steel. However, the problems of bonding magnesium to steel are quite different. There is a great deal of activity between aluminum and steel and the principal problem in the past has been to reduce or limit this activity. On the other hand, in the case of magnesium, there is only limited chemical affinity to steel so that the problem is not in reducing or limiting their activity, but to encourage it. In this connection, it is interesting to note that at present there is no available equilibrium diagram for magnesium iron although there is one for aluminum iron.

It is, therefore, an object of this invention to provide a bond between magnesium and steel or iron that will not come apart upon deformation.

It is a further object of the invention to provide a method for cladding magnesium in its solid state to ferrous articles.

To the accomplishment of the foregoing and related ends, said invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

Broadly stated, this invention relates to a method of cladding magnesium to ferrous articles that includes the step of providing the ferrous articles with a coating of metal soluble in magnesium, and urging the magnesium and ferrous articles together under an atmosphere of a noble gas.

In carrying out the method, if the surface of the ferrous article to be coated is not already substantially free from foreign matter, it may be cleaned in any suitable manner such as by pickling, wire brushing, or sand blasting. Pickling is the preferred form and may be accomplished by a dipping in a 15% aqueous solution of hydrochloric acid, although other ways are known which may be used.

The cleaned ferrous metal surface is then plated or coated with a thin coat of metal soluble in magnesium, such as copper, nickel, tin, zinc, aluminum, beryllium, cadmium, cobalt, lead, silicon, or silver, by an electroplating step or other suitable coating Operation. This coating provides an area of increased solubility with respect to the magnesium whereby the ferrous base is left clean to form a bond with the magnesium by virtue of the solution activity of said coating.

The thickness of the coating metal on the ferrous article may range from 0.0001 inch to 0.0010 inch, although about 0.0002 inch is the usual thickness ordinarily employed.

The magnesium article or material may be commercial grades of magnesium or a magnesium base alloy.

The magnesium is cleaned by dipping it in muriatic acid, washing with water, and air drying. The surface of the magnesium may be scratched with a wire brush after drying. Alternatively, the magnesium may be cleaned by bufiiing with a wire wheel and blowing OK the fine particles with air.

In carrying out the method, the ferrous metal article, having a thin coat of copper, nickel, tin, zinc, aluminum, beryllium, cadmium, cobalt, lead, silicon, or silver is placed against the magnesium with the surface of the ferrous article having the coating metal contacting the magnesium. Ordinarily, the materials are then heated to an elevated temperature, below the melting point of the magnesium, under an atmosphere of a noble gas. At the same time the magnesium and ferrous articles are urged together so as to achieve solid surface bonding at the interface.

It is critical to the present invention that the heating and bonding take place under the atmosphere of a noble gas. The noble gases include helium, neon, argon, crypton, Xenon, or mixtures of the foregoing.

The temperature must be suificiently high to cause the coating metal to diffuse into the magnesium, ordinarily just below the melting point of the magnesium article. The temperature must be below the melting point of the ma nesium material for bonding in the solid state. Usually the temperatures will range from about 600 F. up to about 1200 F. In carrying out the bonding the ferrous metal article and magnesium may be clamped together under pressure and placed in a chamber containing a noble gas. The chamber is then heated to the proper elevated temperature. The assembly is then allowed to cool in an atmosphere of a noble gas.

The process may also be carried out continuously in which case the ferrous article and magnesium are passed between a pair of rollers which urge them together under an atmosphere of a noble gas at elevated temperatures.

if magnesium alloys are used, the temperature will normally be lower than that for pure magnesium. The primary requisite is to raise the temperature to an amount suflicient for the coating metal to diffuse into the magnesium material without melting the magnesium material. In any case, the melting point of the magnesium is the upper temperature limit for the process.

The following example is given by way of illustration of the process and should not be construed in any way as limiting the present invention, except as defined by the appended claims.

Example A sheet of steel was cleaned by degreasing with trichloroethylene followed by a mild alkaline anodic and cathodic cleaning with a water rinse, a 60 Baum sulphuric acid cleaning with a water rinse followed by copper plating for ten minutes at 20 amperes per square foot in a copper cyanide solution to a coating of 0.0002 inch of copper. The copper coated steel sheet was then rinsed in water and dried.

A sheet of magnesium was cleaned by dipping in hydrochloric acid, washing under water, and drying in air. The surface was scratched with a wire brush.

The magnesium sheet was placed against the surface of the steel sheet having the coating of copper, and the two sheets urged together with a slight amount of pressure with a C-clamp. This assembly was then placed in a chamber which was provided with an atmosphere of an inert gas and then heated to about 1100 F. The article formed by this process of the invention does not come apart at the bond when deformed. A micrograph of the bond showed that a eutectic compound had been formed 9 at the inner surface by diffusion of the coating metal into the magnesium.

This application is a division of application Serial No. 557,244, filed January 4, 1956, now Patent No. 2,911,710.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

We therefore particularly point out and distinctly claim as our invention:

1. As new article of manufacture, a magnesium base article, a ferrous article, said ferrous article directly bonded to said magnesium article, and a metal substantially completely diffused into said magnesium at the interface of said magnesium and ferrous articles selected from the class consisting of nickel, copper, and silver.

2. The new article of claim 1 wherein said metal diffused into magnesium is nickel.

3. The new article of claim 1 wherein said metal diffused into magnesium is copper.

4. The new article of claim 1 wherein said metal diffused into magnesium is silver.

5. A lamina comprising magnesium base article of a thickness of at least 0.03 inch, a ferrous article directly and integrally clad to said magnesium article, and a metal which is diffused into said magnesium at the interface of said magnesium and ferrous articles, said latter metal selected from the class consisting of copper, nickel, and silver.

6. The new article of claim 5 wherein said metal diffused into magnesium is copper.

7. The new article of claim 5 wherein said metal diffused into magnesium is nickel.

8. The new article of claim 5 wherein said metal soluble in magnesium is silver.

References Cited in the file of this patent UNITED STATES PATENTS 2,473,888 Jordan June 21, 949 2,478,478 rebe Aug. 9, 1949 2,486,936 Fergus Nov. 1, 1949 2,735,163 Brooks Feb. 21, 1956 

1. AS NEW ARTICLE OF MANUFACTURE, A MOGNESIUM BASE ARTICLE, A FERROUS ARTICLE, SAID FERROUS ARTICLE DIRECTLY BONDED TO SAID MAGNESIUM ARTICLE, AND A METAL SUBSTANTIALLY COMPLETELY DIFFUSED INTO SAID MAGNESIUM AT THE INTERFACE OF SAID MAGNESIUM AND FERROUS ARTICLES SELECTED FROM THE CLASS CONSISTING A NICKEL, COPPER, AND SILVER. 